feat(telegram): add deleteMessage action

Add ability to delete messages in Telegram chats via the message tool.

Changes:
- Add deleteMessageTelegram function in send.ts
- Add deleteMessage action handler in telegram-actions.ts
- Add delete action support in telegram message plugin adapter
- Add deleteMessage to TelegramActionConfig type
- Update message tool description to mention delete action

Usage:
- Via message tool: action="delete", chatId, messageId
- Can be disabled via channels.telegram.actions.deleteMessage=false

Limitations (Telegram API):
- Bot can delete its own messages in any chat
- Bot can delete others' messages only if admin with "Delete Messages"
- Messages older than 48h in groups may fail to delete

src/agents/tools/message-tool.ts

@@ -148,7 +148,7 @@ export function createMessageTool(options?: MessageToolOptions): AnyAgentTool {
     label: "Message",
     name: "message",
     description:
-      "Send messages and channel actions (polls, reactions, pins, threads, etc.) via configured channel plugins.",
+      "Send, delete, and manage messages via channel plugins. Supports actions: send, delete, react, poll, pin, threads, and more.",
     parameters: schema,
     execute: async (_toolCallId, args) => {
       const params = args as Record<string, unknown>;